In the related art, Patent Literature 1 is known as an example of a technical document of this technical field. Patent Literature 1 discloses a viewpoint location measurement device that measures a viewpoint location of a driver based on the angles of the rear-view mirror and side-view mirrors of a vehicle. In this viewpoint location measurement device, straight lines extending from the multiple mirrors to the viewpoint location of the driver are obtained based on the angles of the rear-view mirror and the side-view mirrors, and an intersection point between the obtained straight lines and a center plane of a driver's seat is measured as the viewpoint location.